Hobbing machine



July 25, 1939. B. R. PURVIN 2,167,267

HOBBING MACHINE Filed April 23, 1956 v 5 Sheets-Sheet l 5 Sheets-Sheet 2 B. R. PURVIN HOBBING'MAGHINE Filed Apil 23, 19:56

July 25, 1939.

lNvENToR Benjamn R d .5mm

Puh/in #MJA-4 A RNEYS l July 25, 1939. B. R. PuRvlN 2,167,267

HOBBING MACHINE n Filed April 23, 1936 5 Shee'S--Sh'eeI 3 l i l INVENTOR Bery'amir/ R. 'Pam/in y www ATTORNEYS `Iuly 25, 1939. B.-R. PURVIN V HOBBING MACHINE Filed April-23, 195e 5 sheets-sheet 5 INVENTOR .Be/gamin R. Fury/'n BY AT ORNEY5 v I Patented July 2s, '1939 UNITED STATES .PATENT oFFicE amaze? noname MAcnmE Benjamin R. Purvimockford, Ill., assignor to Barber-ColmanV Company, Rockford, Ill., a. corporation of Illinois Application April 23,1936, serial ivo. '15,949

8 Claims. (Cl. 90%)' `adjustment is a headstock I I rotatably supporting The present invention relates to improvements in variable speed feeding mechanisms forma-- chine tools, and has particular reference to anew and improved mechanism for effecting a '5 relative translatory feed between a work spindle and a tool spindle rotatable in timed relation, as-

for example in hobbing machines.

One of the objects of the invention resides in the provision of a novel variable speed feeding vlll for the .cuttingof either spur or helical gears.

A further object resides in 4'the provision .of aI new and improved feeding mechanism for hobbing machines which is flexible in character, and adjustable to vary the rate of feed in finely gradu- 2li 'ated increments over the entire range.

Still another object resides in the provision, in a machine, for hobbing helical gears or the like wherein the timed rotation of the spindles is adiusted in accordance with the relative axial feed to compensate for the lead of the gear teeth, of

a novel feeding mechanism which not only is adjustable to vary the rate of feed over a finely graduated range, but which also maintains an accurate and positive time( relation between the com.-

v pensatory adjustment and the feed in all positions of .feed adjustment.

Further objects and advantages-will become apparent as the description proceeds.

In the accompanying drawings,

A Fig. l1 is a front elevational View, partiallyY in section andpartiallybroken away, of abobbing vmachine with a feeding mechanism embodying the features of my invention. 1

' 2 is a plan view of the machine.

. v Fig.l 3 isa fragmentary leftv end view on'an enlarged scale and partially sectioned.

Fig. 4 is a fragmentary transverse sectional view embodiment of .the'invention is shown incorporated in a hobbing machine comprising an elongated base 1 with longitudinal ways 8 on thetop.

' Anr upright column 9. with parallel vertical w'ays I6 onthe front, is fixed ^on one end of the base 1. Slidably mounted on the ways I0 forvertical Aways I8 on the underside.

a horizontal spindle I2 .extending longitudinally of the ways 8. In the present instance, the means for adjusting the headstock II comprises a non-A rotatable vertical screw I3, with the lower end 5 engaged against a stop on the base 1, and in threaded engagement intermediate'its ends with a nut I'4 rotatably mounted on the rea'r of the headstock. The nut is in the form of a worm wheel meshing with a Worm I5 on a shaft I6 jour- 10 naled in and extending to the front of the head- 'stock Il for manual actuation.

The headstock I I is' rigid with an elongated over arm I1 which extends longitudinally over the base 1, and which has parallel longitudinal l5 'I'he free end of the over arm I1 is rigidly attached to a block I9 vertically adjustable in an end support 20 adjustably mounted on the ways 8. A tailstock 2| having a center 22 in axial alignment with the spindle 20 I2 is mounted on the ways I8 for adjustment along the arm I1.

Preferably, the spindle I2 is employed to support and rotate the work, which is herein disclosed as a spiralgear blank A mounted on an arbor 25 clamped in the spindle and against the center '22. Mounted for power translation'on the ways 8 between the column 9 and the end support 20 is a tool support 23 comprising a saddle 24 directly engaging the ways andy having a depending lug 30 25 in which a fixed nut 26 is secured. A screw 21, in threaded engagement with the nut 26, is journaled at its ends in the base 1, and is adapted to be driven from a suitable source of power to translate the saddle 24. A hob swivel 28 is mount- 35 ed on the saddle 24 for angular adjustment about a vertical axis, and has two upstanding bearings `29 and 30 in which a tool spindle 3I'i`s journaled. `The spindle 3l extends diametrically across the' swivel axis, and supports a'` suitable hob B for 40 cutting the gear A.

The work and hob spindles I2 and 3| are ro tated in timed relation from a main drive shaft 32 journaled in and extending to the rear of the base 1. Rotatable on the shaft 32 and adapted to 45 be connected thereto by a clutch 33 is a pulley 34. A belt 35 serves to connect the pulley 34 to a pulley 36 onthe shaft of an electric drive motor 31 within the base 1. The belt ,drive is suitably enclosed4 by a housing 38 on the rear of the base 1. 50

'I'he clutch 33 is adapted to be opened'and closed 'by means of a manual lever 39 operable from the front of the base 1. In the present instance, the lever 39 is connected through a rod 40 to a crank arml4i on a rock shaft 42 journaled in the hous- 56 ing 38. A'second crank arm 43 on the shaft 42 lug 25 on the underside of the saddle 24. The.

gear `41 is connected through a train of gears 48 to 52 to a shaft 53 which isjournaled in the swivel 28, and which is connected through gears 54. and 55 to the hob spindle 3|. The gear 52 is arranged to roll about the gear 5| so that the rotative drive for the hob spindle 3| is connecter` in all angular positions'of the hob swivel 28.

The rotative drive for the work spindle |2 is taken from the shaft 46 through a train of index change gears 56 to 59 mounted in a gear housing 60 on the left end of the base '1, and driving a shaft 6|. The latter, through bevel gears 62 and 63, is connected to the inlet bevelgear-64 of a differential mechanism 65 driving a vertical spline shaft 66 suitably journaled in the base 1 and column 9. This differential mechanism comprises a cage-61 rotatable on the shaft 66 and carrying two bevel gears 68 and 69 both meshing with the gear 64 and a bevel gear 10 on the shaft. A wormwheel 1| rigid with the 'cage 61 and coaxial with the shaft 66 meshes with a worm 12. When the cage 61 is held stationary, the shaft 66 will rotate in timed relation to the shaft 46 as determined by the index change gears 56 to. 59. Rotation ofthe worm wheel 1| will advance or retard the timed rotation of the shaft 66 relative to the shaft 46.

Splined for vertical movement on the shaft 66 is a worm 13 suitably journaled in and adjustable with the-headstock I. The worm 13 meshes with a worm Wheel 14 to complete the drive for the work spindle I2.

One of the primary features of the present invention resides in the provision of a variable speed mechanism, avoiding the use of change gears, for eecting a cutting feed betweena work piece and a tool rotating in timed relation, and -in the instance herein disclosed for rotating the screw 21 to feed the hob B axially of the spindle I2 through the gear blank A. The variable speed mechanism is adjustable over'a nely graduated range from zero to maximum, and hence may be either electrical 'or hydraulic in character. Preferably, an hydraulic transmission is employed, comprising a rotary hydraulic motor 15 having a shaft 16 connected through a worm 11 and'worm wheel 18 to the screw 21. A variable displacement pump 19, driven from the shaft 32- through gears 80 and 8| at a constant speed, is adapted to be reversibly connected to the motor 15 in a closed hydraulic circuit. The details of the motor 15 and the pump 19, per se, form no part ofthe present invention, and hence Vare not disclosed herein. The motor 15 has two fluid transmission conduits, passages or lines 82 and 83 which are adapted to be reversibly connected by a direction and control valve 84 to discharge and return lines 85 and 86 leadingrespectively from and to the* pump 19.v The displacement of the pump 19, and hence the speed of the motor 15,'is adjustable through a shaft 81, bevel gears 88'and 89 and a shaft 90 by a hand wheel 9| from the front of the base 1. v

The direction valve 84 comprises a casing 92 mounted on the front of the base 1, and formed with a closed bore 93. A spool plunger 94 is distral position. v

The lines 85 and 86 from the pump 19 open to the bore 93 respectively midway between the ends and at one end. The lines 82 and 83, from the motor 15, open to the bore 93 respectively at opposite sides of the line 85, and are spaced from the -line 85 by the width of the head 96v and adapted for selective connection therewith respectively 15 through the spaces -98 and 99 upon movement of the plunger 94 into its opposite end positions. The lines 85 and 86,-in the reverse positions of the plunger 94, are also adapted respectively for selective connection through the spaces 98 and 99 with two longitudinally spaced ports |02 and |83 which are controlled by theheads 95 and 91, and which open to a passage |04 in constant communication with the return line 86. An axial bore |05' in the plunger 94 communicates at its outer end through the bore 93 with the. return line 86, and opens at its inner end tothe periphery of the head 96 for registration with the line 85 when the plunger 94 is in neutral position.

The arrangement of lines and ports is such that when the plunger 94 is `in the right-hand position, fluid from the pump 19 will pass through the line 85, the space 98`andv the line 82 to the motor.15, and from the motor through the line B3, the annular space 99, the port |03, the passage |04 and the line 86to the pump to eiect a. feed 'of the saddle 24 in one direction, for example to the left in a cutting stroke. When' the valve plunger 94 is in the left-hand position, the supply of fluid under pressure to the motor 15 is reversed to reverse the direction of`.feed of the saddle. In this position of adjustment, fluid from the pump 19 passes through the line 85, the space 99 and the line 83 to thev motor 15, and froml the motor through the line 82, the space v98, the 4-5 port |02, the passage |04, and the-return line' 86 to the pump. When the valve plunger 94 is in neutral position, the pump is disconnected from the motor, the fluid passing from the line 86, through the bore |05 to thereturn line 86, and the lines82 and 83 being disconnectedboth from pressure and exhaust.

To provide means for' operating the valve 84, one end of the plunger 94 lis rigidly connected .to an axial rod |06 which extends from the casing 92 lfor connection to the lower end of a lever |01 pivoted intermediate its ends on the base 1. The plunger 94 is held releasably in the righthand position, to effect-the cutting feed, by a latch |08 which-is pivoted on the base 1, and 60 which is urged by a tension spring |09 into position for engagement at one end by a shoulder |.|0 on the rod |06. A pin on the other end of the latch |08 is disposed in the path of a dog ||2 adjustably mounted on the saddle 24. .At 65 the endof the cutting stroke,` the dog `||2 will depress lthe pin to disengage the latch |86 from the shoulder ||0, and thereupon the spring arenas? Ilv are rotated in timed relation, and therela- `tionship need not be adjusted in the course of the feed. However, for cutting work pieces, such as the helical gear A, having teeth or projections with a lead, -the rotation of the work'ancl tool spindles lz anaal must be relativen adjusted to compensate for the lead as the feed proceeds. This compensationis enected by driving the differential mechanism 65 in timed relation to the feed. In the present instance, the drive is taken from the shaft 16 which is connected through beveigears H3 and IM to a shaft HI liournaled in the base 1. The shaft lil is connected through lead change gears IIS to lis to a shaft III on which the worm 'I2 is mounted. Different gears IIB to Il! may be substituted for dinerent leads. If the wrk has no lead, the gears are removed to interrupt the drive tothe differential mechanism.

I claim as my invention: l. A bobbing machine comprising, in combination, a work spindle, a tool spindle, means for rotating said spindlesin timed lrelation and including a diiierential mechanismV for adjusting said relation, a mechanical drive for feeding said tool spindle axially 'of said work spindle, a

mechanical drive for said mechanism, a hydraulic motor for operating said drives in timed relation, a variable displacement pump, a direction valve for connectingv said motor and said' pump reversibly in a closed circuit and having a neutral position for short-circuiting said pump, spring means tending to urge said valve out of .either operative position intoneutral position,

an operator for said valve, means for retaining said valve releasably in one operative position,`

and means for tripping said last mentioned means `to release saidvalve formovement into neutral position upon movement of said tool spindle into a predetermined feed position. 2. A hobbing machine comprising, in combination, a work spindle, a tool spindle, means for "rotating said spindles in timed relation, a mechanical drive for feeding said ltool spindle axially of said work spindle. a reversible hydraulic motor for operating said drive, a variabledisplacement pump, a direction valve for c onnecting said motor and said pump reversibly 'in a closed circuit and having a neutral position for short-circuiting said pump. Spring means tendingto urge said valve out of-v either operative -position intoA neutral position, an operator for said valve, means for retaining said valve revl'easably in one operative'position, and means for tripping said last mentioned means to release said -valve .for movement into neutral position upon/movement of said tool spindle into s predetermined feed position.v

3. A bobbing-machine cnprising, in combination. a work spindle, a tool spindle, means for rotating said spindles in timedrelation, amechani drive for feeding said tool Spindle azi-l' -ally-ot said work spindle, a reversible hydraulic one direction motor for operatingsaid drive; at variable displacement constan responseto into a predetermined eect movement of said into said -'4 Ah0bhingmachine comprisingv'in m' mmsweawhmnmmmt `draulilc transmisslonfor vat'ing'saiddrlveand mission for operating said mechanical means,

said transmission including a hydraulic motor, means for supplying pressure fluid invariable 15 amounts over a finely 'graduated range from zero to maximum, and valve means for operatively connecting said motor to said last mentioned means. s"

5.A hohbing machine comprising, in combi- 20 nation, a work spindle, a tool spindle, means for rotating said spindles in timed relation and including a dinerential mechanism for adjusting said relation. a mechanical drive for feeding said tool spindle axially of saidv work spindle, `a mechanical drive for said mechanism, a hydraulic motor for operating said drives in timed relation, a. variable displacement pump, and a direction valve for connecting said motor and f said pump reversibly in a closed circuit.

6. A hobbing machinecomprising, in combination, a work spindle, a tool spindle, means for rotating' said spindles in timed relation, a.. mechanical drive for vrelatively feeding said tool spindle axially of said work spindle, a hydraulic u motor foroperatng said drive, a pump, a direction' valve for connecting said pump reversibly to ,said motor and having a Vneutral position in"- whichy said connection is interrupted, spring means tending tov urge said valve out of either operative position into neutral position, an operatoi' for said valve, means for retaining said valve releasably in one operative position', and means for tripping said last mentioned means to release said valve for movement into neutral poa sition upon movement of said tool spindle into a predetermined feed 7. A hobbing machine comprising, in combination, a work spindle, a heb spindle. means forrotating said spindles in 'a normal timed relation to maintain the work and the hob propermeshingengagement.meansforfeeding' said spindiesrelatively to'each other in a-directionarially'ofsaidworkspindlaandahydrivingsaidlastmentionedmeanaldd'hydramictransmissionbeing available atwill formoiifyillgthe timedrelationofsaidsplndlesindennitetimedrelation totherelativefeedosaidspindleswherebyto Acompensatefortheinclinaticiiofthegearteetlru when bobbing gears with a tooth lead.

A hobbing machine fcomprlsing, in combination-a work spindle. 's tool spindle, means forrotatingsaidspindlesinpositivetimedrelation, a mechanical drive without change gears -u for feeding said dies relatively to eachother, mechanical means available at will for'adiusting the rotative said spindles, a reversible hydraulic motor for oper- .said mechanical means in pxuveamedremumwmauedeuverypump, and' control| means fot operatively connecting I saidpumpreversibiytossidmotor. 

